4 gallons of water is needed to dilute to a concentration of 10%.
<u>Step-by-step explanation:</u>
It is given that,
The 5 gallons of water contains 18% of acid solution.
Now, we are asked to find the gallons of water needed to dilute it to a concentration of 10% acid solution.
We obtain the equation by stating that the amount of acid 10% in the water must dilute up to 18%.
For this, x amount of water should be added.
Therefore, the equation is framed as,
⇒ 0.1 (x+5) = 5 (0.18)
⇒ 0.1x + 0.5 = 0.9
⇒ 0.1x = 0.9 - 0.5
⇒ x = 0.4 / 0.1
⇒ x = 4
∴ 4 gallons of water is needed to dilute to a concentration of 10%.
